Device for adjusting the slope of a chair back

ABSTRACT

The device comprises a hollow casing, supported by the seat frame of a chair and delimiting two opposed truncated bearings on which are applied, by the action of at least one resilient recoil member, two truncated cones, also opposed, loosely screwed on to a large pitch helicoidal grooved common rod, an operating member controlling, against the action of the resilient member, the simultaneous loosening of the truncated cones in relation to the truncated bearings.

United States Patent Inventor Jean-Claude Andre Bertin Route d Evecquemont, V., Vaux-sur-Seine, France Appl. No. 9,687 Filed Feb. 10, 1970 Patented Jan. 11, 1972 Priority Feb. 13, 1969 France 69/0345 1 DEVICE FOR ADJUSTING THE SLOPE OF A CHAIR BACK 4 Claims, 4 Drawing Figs.

U.S. Cl 297/375, 297/359, 74/531, 188/67, 248/412 Int. Cl..'. A47c 3/00, B60m1/02,F16m 11/00 Field of Search 297/374-375,

[56] References Cited UNITED STATES PATENTS 2,928,621 3/1960 Cohn .1 279/2 X 3,048,416 8/1962 Rogers 279/2 2,252,097 8/1941 Rockenfield 4 297/375 2,750,994 6/1956 Howell 297/375 FOREIGN PATENTS 528,038 4/1954 Belgium 248/412 1,449,684 7/1966 France Primary Examiner-Paul R. Gilliam AItorney-Jmirie & Smiley ABSTRACT: The device comprises a hollow casing, supported by the seat frame of a chair and delimiting two opposed truncated bearings on which are applied, by the action of at least one resilient recoil member, two truncated cones, also opposed, loosely screwed on to a large pitch helicoidal grooved common rod, an operating member controlling, against the action of the resilient member, the simultaneous loosening of the truncated cones in relation to the truncated bearings.

DEVICE FOR ADJUSTING THE SLOPE OF A CHAIR BACK The present invention relates to devices inserted between the seat and back of chairs to enable the slope of the back to be adjusted.

Most of these devices consist of offset sector straight or curved, toothed pinion or gearing devices and are also generally made for being entirely incorporated in at least one of the hinges of the back on the seat, the other hinge being, in such case, connected to a recoil spring, intended when the mechanism is out of action, always to return the back to its original position for which it extends, for instance, perpendicular to the plan of the seat.

For various reasons, the above-mentioned devices do not give complete satisfaction. Actually, devices of the ratchet type only afford certain possibilities of slope adjustments which do not systematically correspond to the morphology of users. Furthermore, devices enabling adjustment to be obtained in any position comprised between extreme abutment positions are not very strong and generally actuated by a very geared-down control which, consequently, requires a large number of turns for obtaining complete tipping of the back, in particular in the case of a seat that can be converted into a bed. Also, all these devices are very expensive, for it is necessary for them to be accurately machined and with very strict tolerances in manufacturing, so as to reduce or eliminate play, either while manufacturing or machining, which are otherwise transmitted in an alternating manner to the level of the back.

The present invention obviates the above-mentioned disadvantages by creating an new device whose design, particularly simple but strong, requires practically no tricky machining or surface treatment, thus permitting mass production to be obtained at a low unit price.

Moreover, the purpose of the invention is designed so that the applying of stresses, in one direction or the other, tends to strengthen the locking of the back in the position chosen, by then affording all safety guarantees, in particular, in the case where the chair is installed in any kind of vehicle.

According to the invention, the device for adjusting the slope of a chair back is characterized in that it comprises a hollow casing, supported by the seat frame of a chair and delimiting two opposed truncated hearings on which are applied, by the action of at least one resilient recoil member, two truncated cones, also opposed, loosely screwed on to a large pitch helicoidal grooved common rod, made integral with the back frame and passing through, from one side to the other, the casing which supports an operating member controlling, against the action of the resilient member, the simultaneous loosening of the truncated cones in relation to the truncated bearings.

Various other characteristics of the invention will moreover be revealed by the detailed description which follows.

Embodiments of the invention are shown, by way of nonrestrictive examples, in the accompanying drawings.

FIG. 1 is an elevation section, partly cut away, of the device according to the invention.

FIG. 2 is a cross section taken substantially along the line II--II of FIG. 1.

FIG. 3 is a longitudinal section taken substantially along the line lII-lIl of FIG. 1.

FIG. 4 is a partial elevation section showing an alternative embodiment of the device.

According to FIGS, 1 to 3, the device according to the invention, comprises a casing I, formed of two semicylindrical half-shells 2 and 3, assembled according to a longitudinal joint plan by means of rivets, screws or other fixing members 4, traversing flanges 5 and 6 fonned by the two half-shells. The half-shell 2 is extended externally in its transversal middle zone, by a pivot 7 extending perpendicularly to the joint plan to be mounted revolving in a bearing 8 formed by a stay plate 9 made integral with a cheek 10 carried by the seat frame of the chair for ensuring by a spindle 11 the hinge of a mobile cheek 12 fixed on the seat frame of the chair back.

The half-shells 2 and 3 are made so as to define between them, after assembling and level with their terminal parts, two truncated bearings 13 and 14 of similar conicity opposed by their large bases. The bearings 13 and I4 fonn bearing seatings for truncated cones I5 and 16 with the same conicity loosely screwed so as to revolve opposite one another on a cylindrical rod 17 having at least one helicoidal large pitch groove or furrow I8, machined for accommodating the sectors of complementary threads 15a and formed by the truncated cones I5 and 16. The rod 17 can be guided in bearings 19 and 20 defined by the half-shells 2 and 3, so as entirely to traverse the casing 1 along the longitudinal axis, beyond which one of the ends of the rod 17, is connected by a hinge spindle 21 to the mobile check 12. The truncated cones l5 and 16 are extended from their large bases by a cylindrical stem 22 or 23 forming a flared collar 24 or 25 on the end. Thesecollars form the bearing members for the ends of a spring 26, of the helical type, for instance, working under compression, concentrically slipped on the rod 17, so that its actions tends always to apply the truncated cones I5 and 16 against their respective bearings 13 and 14.

The truncated cones I5 and 16 are connected to an operating member 27 enabling their simultaneous separation in relation to the truncated bearings 13 and 14 against the action of the opposing spring 26. The operating member 27 consists of a fork 28 whose base 29 is hinged in a vertical plan on a pivot 30, extending from the inner face of the half-shell 3, substantially in the cross middle zone of said half-shell 3 and perpendicularly to the joint and assembly plan with the half-shell 2. The base 29 is extended by two arms 31 and 32 that are opposed, so shaped as to extend towards the inside of the casing 1, respectively towards the top and bottom part of said casing, in considering a vertical plan passing through the assembly plan of the two half-shells 2 and 3. Still looking at this plan, the arms 31 and 32 are extended by two horizontal parts 33 and 34, comprising, at the end, in a perpendicular direction, two curved fingers 35 and 36 directed opposite to each other. The fingers 35 and 36 have an inner profile chosen so that, in the inoperative position of the member 27 shown in FIG. 1, their terminal parts cooperate with two convex annular bearings 24a and 25a defined by collars 24 and 25.

The base 29 of the fork 28 forms or comprises a stud 37 for assembling an operating rod 38 passing through a slot 39 made, for this purpose, in the wall of the half-shell 3. The part of the operating rod 38, outside the half-shell 3, preferably extends in a plan superimposed on the casing 1 so as to be made easily accessible for the person in the chair. A recoil spring 40, of the helicoidal type for instance, effecting a pull, is placed between the rod 38 and half-shell 3 so that its action always tends to make the rod 38 pivot in the direction for which the fingers 35 and 36 are applied by their terminal parts against corresponding convex an'nular bearings 24a and 25a.

The device described above, works in the following manner:

In the position shown in FIG. 1, the spring 26 applies the truncated cones 15 and 16 against the bearings 13 and 14 which oppose all free rotation of said cones thus effecting the axial locking of the rod 17. When the frame of the back is impelled in the direction of the arrow f,, for instance under the action of the recoil spring normally incorporated level with the second hinge of the back or under the action of an impact, in particular, in the case of applying the chair to a vehicle, the pivoting of the mobile cheek 12 in the same direction, tends to thrust the rod 17 which ensures a harder application of the truncated cone 15 against the corresponding truncated part 13. The truncated cone 15 is thus more firmly locked in rotation, and consequently opposes any possibility of the rod 17 sliding, which holds the mobile check 12, and hence, the back frame in the selected angular position. It should be noticed that the spring 26 sets up a regular compensation of any play likely to exist between the difierent parts forming the device, thus limiting the amplitude of clearance likely to be transmitted to back frame, solely to the value of existing clearances level with the pivot 7 and spindles 21 and 11. Furthermore,

the tendency of the rod 17 to thrust the truncated cone 15 has no influence whatever on the position of the truncated cone 16, even in the contingent case of play to be compensated, seeing that this truncated cone is automatically pressed against the corresponding bearing 14 by the action of the spring 26.

The device obviously has the same characteristics in the case where the back frame is impelled in the direction of the arrow f,, either by the weight of the user's body, or by an impact or acceleration in the case of applying the chair to a vehicle.

In all cases, we are thus certain of obtaining a locking that is the more firm and efficacious as the stress exerted on the back is great.

When requiring to alter the position of the back for giving it, for instance, an angular orientation greater than what it has, the user acts on the rod 38 of the operating member 27 in the direction of the arrow f for revolving the pivot 30. As can be seen in FIG. 1, the fingers 35 and 36 act simultaneously like two ramps on the convex annular bearings 24a and 25a and in this way, control, against the action of the resilient member 26, the axial coming together of the truncated cones l5 and 16 which are thus separated in relation to the bearings 13 and 14. To obtain the simultaneous separating of the truncated cones l5 and 16, it is only necessary to overcome the resistance of the spring 26, so that the pressure applied by the fingers 35 and 36 is relatively slight and cannot, in any case, oppose the free rotating of the truncated cones 15 and 16. The withdrawing of the cones in relation to the bearings 13 and 14 has the effect of unlocking the device so that the user can, by exerting in the direction of the arrow f, a pressure just sufficient to overcome the action of the recoil spring 26, cause the back to pivot in the corresponding direction for entailing the axial displacement of the rod 17 in the direction of the arrow f,. The

displacement of the rod 17 is actually made possible, by

separating the truncated cones 15 and 16, which, during this displacement, are made to rotate on themselves by the reaction of the helicoidal groove 18 on the thread sectors 15a and 16a. The rotation of the cones l5 and 16 has no influence on the position they occupy, as the fingers 35 and 36 remain in regular cooperation with the peripheric collars 24 and 25.

When the back assumes the new position chosen, the user releases his action on the rod 38 which is returned to its original position by the spring 40. The fingers 35 and 36, are, in this way, released in relation to the collars 24 and 25 and then free the truncated cones 15 and 16, which, under the action of the spring 26, are simultaneously applied against the truncated bearings 13 and 14, being obviously subjected to a slight rotation on the rod 17 by the reaction of the thread sectors 15a and 16a in relation to the helicoidal groove 18. The device then takes its normal inoperative position, i.e., as shown in FIG. 1, in which it again effects the firm and efficacious locking of the back in the new position chosen.

When it is required to bring the back towards its normal abutment position, the users acts on the rod 38 in the direction of the arrow f;,, for controlling, as formerly, the simultaneous separating of the truncated cones 15 and 16 in relation to the bearings 13 and 14. The user then relieves the applying of his own weight on the back, so that the preponderating action of the recoil member normally provided brings said back in the direction of the arrow f,. As before, the truncated cones l5 and 16, freed in rotation, enable the axial displacement of the rod 17 in the reverse direction to that of the arrowfii during which displacement they are subjected to a rotation on themselves.

As can be seen from the foregoing, the actuating of the operating member 27 is obtained by always acting in the same direction on the rod 38, so that the user is not obliged to make any effort to adapt the adjusting of the slope of the chair, even when he is not familiar with the device according to the invention. it should also be noticed that the actuating of the rod 38 takes place in all cases in the direction of the arrowfa which corresponds to a reflex action not requiring any reflecting effort on the user's part.

Among the various advantages of simplicity, strength and play compensation, it should be noticed that the device enables the back of the chair to be locked in any position likely to be occupied between the normal abutment position and the maximum sloping position.

FIG. 4 shows an alternative embodiment according to which the device comprises a casing 41 formed of two half-shells 42 and 43 assembled in a similar manner to the two half-shells 2 and 3. The half-shells 42 and 43 are made so as to form between them and inside the casing that they make, two truncated bearings 44 and 45 impelled against each other by their small bases, on either side of a middle transversal bore 46 having a distinctly inferior diameter to that ofthe internal section of the casing 41. The bearings 44 and 45 form bearing seatings for two truncated cones 47 and 48 screwed on to a rod 49 similar to the rod 17. The truncated cones 47 and 48 are applied on their respective truncated bearings by two helicoidal springs working under compression 50 and 51 concentrically threaded on the rod 49 for bearing against the large bases of the truncated cones 47 and 48 and against the lateral walls 52 and 53 closing the ends of the casing 41. As shown at the righthand side of FIG. 4, the lateral walls can be directly made by the half-shells 42 and 43, or contingently, as shown on the lefthand side, by a plug simultaneously mounted on the half-shells 42 and 43. In such a case, it would be possible to give to the plug forming the wall 52 a bearing 54 for guiding the rod 49. Such bearing could also form a centering member for the corresponding end of the spring 50.

The truncated cones 47 and 48 are connected to an operating member 55, comprising, for instance, an oval cam 56 revolvably mounted on a pivot 57 projecting from the peripheric face of the bore 46, so that the cam 56 extends perpendicularly between the small bases of the truncated cones 47 and 48 and parallel to the rod 49. The cam 56 is connected with an operating rod 58 shown in dotted lines, passing through the corresponding half-shell by means of a slot made for this purpose, in a similar manner to that of the slot 39 of the preceding example.

For unlocking the device made as shown in FIG. 4, it is only necessary to act in the direction of the arrow f on the rod 58, so as to revolve the cam 56 in the direction where it causes the relative separating of the truncated cones 47 and 48 and their simultaneous loosening in relation to the bearings 44 and 45. The recoil of the truncated cones 47 and 48 with a view to releasing the rod 49 takes place against the action of the resilient members 50 and 51, which again apply the cones 47 and 48 on their respective bearings, when the user stops its action in the direction of the arrow f on the rod 58.

In certain cases, the truncated bearings and/or the truncated cones can comprise a friction packing.

1 claim:

1. A chair back adjusting mechanism comprising a casing defining a first pair of spaced brake elements, a rod moveably mounted in and extending through said casing and said brake elements, a second pair of brake elements moveably mounted on said rod within said casing, spring means in said casing normally urging said second pair of brake elements respectively into braking engagement with said first pair of brake elements, means between said rod and said second pair of brake elements to retain said rod against movement when said first and second pairs of brake elements are in braking engagement, and control means in said casing for engaging the facing portions of said second pair of brake elements to move said ele ments in opposition to said spring means to disengage said second brake elements from said first brake elements and permit adjustment of the mechanism, said control means including an operating member externally of said casing, said first pair of brake elements comprise truncated conical brake drums, said second pair of brake elements comprise truncated brake shoes, and said rod retaining means comprises interengaging threads on said shoes and rod, said rod extending axially through said shoes.

2. A mechanism according to claim 1, wherein said drums are in the end portions of said casing with their large bases in facing relation, said shoes each having a grooved collar extending from its large base portion, and said control means comprising a yoke pivotally mounted in said casing on an axis perpendicular to said rod, said yoke having cam means on its arms respectively engaged in the grooves of said collars.

3. A mechanism according to claim 1, wherein said drums are in the intermediate portion of said casing with their smaller ends in adjoining relation and defining a through opening for said rod, the smaller ends of said shoes being in facing relation and being urged toward each other by said 

1. A chair back adjusting mechanism comprising a casing defining a first pair of spaced brake elements, a rod moveably mounted in and extending through said casing and said brake elements, a second pair of brake elements moveably mounted on said rod within said casing, spring means in said casing normally urging said second pair of brake elements respectively into braking engagement with said first pair of brake elements, means between said rod and said second pair of brake elements to retain said rod against movement when said first and second pairs of brake elements are in braking engagement, and control means in said casing for engaging the facing portions of said second pair of brake elements to move said elements in opposition to said spring means to disengage said second brake elements from said first brake elements and permit adjustment of the mechanism, said control means including an operating member externally of said casing, said first pair of brake elements comprise truncated conical brake drums, said second pair of brake elements comprise truncated brake shoes, and said rod retaining means comprises interengaging threads on said shoes and rod, said rod extending axially through said shoes.
 2. A mechanism according to claim 1, wherein said drums are in the end portions of said casing with their large bases in facing relation, said shoes each having a grooved collar extending from its large base portion, and said control means comprising a yoke pivotally mounted in said casing on an axis perpendicular to said rod, said yoke having cam means on its arms respectively engaged in the grooves of said collars.
 3. A mechanism according to claim 1, wherein said drums are in the intermediate portion of said casing with their smaller ends in adjoining relation and defining a through opening for said rod, the smaller ends of said shoes being in facing relation and being urged toward each other by said spring means which are in the end portions of said casing, and said control means comprising a cam pivotally mounted in said through opening for engagement with said shoes to move the latter out of engagement with said drums.
 4. A mechanism according to claim 1, in combination with a chair comprising a seat frame and a back frame pivotally mounted on said seat frame, said casing being mounted on said seat frame and one end of said rod being connected to said back frame. 